Heretofore, there has been proposed an apparatus for measuring the toe angles of the wheels of a vehicle while reflecting a deviation in a rotational direction as viewed in plan of the vehicle that has been set in place. The apparatus has measuring units placed outwardly of the respective four, i.e., front right, front left, rear right, and rear left, wheels of the vehicle (see, for example, Japanese Laid-Open Patent Publication No. 6-109462).
Each of the measuring units of the apparatus has a measuring means including a support rod which is movable forward and rearward. The support rod has on its distal end a tiltable detection plate for contacting the outer side of a wheel. The measuring unit calculates a corrective angle β indicative of a tilt angle of the vehicle around the center of the apparatus in its entirety, from the distance that the support rod has moved forward when the detection plate contacts the wheel. Thereafter, the corrective angle β is subtracted from the tilt angle of the detection plate of each of the measuring means, thereby calculating the toe angle of each of the wheels. In this manner, a change in the toe angle due to a positional deviation of the vehicle can be compensated for.
The apparatus disclosed in Japanese Laid-Open Patent Publication No. 6-109462 determines a corrective angle θ indicative of a tilt angle of the vehicle based on the distance that the support rod has moved forward. Therefore, if the corrective angle θ is excessively large, then the support rod may not be able to move sufficiently forward, making it difficult to measure the toe angle. Even when the corrective angle θ is nil, if the vehicle is extremely displaced to the left or right, then the same difficulty tends to occur.